runout triggered on early layers

I have a print that has a fairly sizeable first layer, and have been using 5 solid layers on top and bottom for this print. The print has a strong tendency to clog up the nozzle during these first layers, and I'm trying to figure out why. I've considered: - overextrusion with a lot of back-pressure from the smooth print bed (EM=0.8) - issues with the silk filament - I recall that silk filaments tend to clog when there are lots of retractions, and while I've considered overriding the retraction length to 0, the fact is, there aren't very many retractions going on for these solid layers. Anyone have any thoughts or suggestions?